In apparatus that employ a moving web, which is transported from one position in the apparatus to another position in the apparatus, it is in many applications desirable to continuously clean the surface of the web of foreign materials. This is particularly true in tape-drive systems such as for magnetic tape recorders, wherein the tape is usually drawn from a supply roll, over a tape guide, over a transducing head, and hence onto a takeup roll. Since the magnetic tape is in repetitive contact with mechanical surfaces, the tape is stressed in such a manner that its oxide coating will shed particles. These small particles adhere to various surfaces, such as the surface of the head or the guiding mechanism. These loose particles may then come in contact with the magnetic tape and are redeposited or accumulate on the recording surface. Successive passages of the tape over a sliding surface in contact with the recording surface of the tape, such as the head, may impact-weld the oxide particles onto the tape-recording surface and/or the sliding contact surface.
In a tape transport system with a peripheral belt drive such as disclosed in U.S. Pat. No. 4,172,569 to Chester W. Newell, the oxide-recording surface faces outward on the tape roll and contacts the belt drive. Any loose particles caught between the belt and the tape will be embossed onto the tape-recording surface.
The buildup of oxide on the tape surface may cause the tape to come out of contact with the head over a large enough area that a signal dropout will occur with respect to information recorded at that area. Particles accumulating on the magnetic transducng head surface may upon impact weld to the head surface causing a buildup of oxide. This oxide buildup will eventually lift the tape away from the head transducing gap, thus reducing the amplitude of the signal transduced from the recorded information because of the tape-to-head separation. Furthermore, the oxide buildup on the head surface will present a rough surface to the tape and accelerate tape wear.
Prior U.S. Pat. Nos. 3,683,445 to Hagadorn, and 3,745,602 to Beistle, disclose tape-cleaning heads which have a body portion with an arcuate surface around which tape is partially wrapped, with an opening formed in the body, a knife edge, or edges being provided in the opening. The knife edges provide a scraping surface to clean the tape as the tape moves toward the knife edge, in either direction.
In Hagadorn the knife blade protrudes slightly out of the cavity so that it presents a cleaning edge to the tape surface in either direction of tape travel. As particles are scraped from the tape they fall into the cavity and are sucked out by means of a vacuum source.
In Beistle a similar structure is employed, the blade in the cavity being movable so that it rocks back and forth as tape direction changes, to thereby present a sharper angle to the tape surface.
Both Hagadorn and Beistle have the disadvantage that the knife edges tend to dull rapidly with time due to tape friction, and the geometries of the cleaning devices. Furthermore, when tape motion stops, particles have built up at the knife edge, and as tape direction reverses, any line of debris at the knife edge will be carried away by the tape. This debris will not be removed by the cavity outer wall, and will be embossed onto the tape surface.
It is, therefore, a primary object of the present invention to provide a tape cleaner that will remove loose oxide particles from a tape surface.
It is a further object of the present invention to provide a tape cleaner that will remove loose oxide particles from magnetic recording tape and deposit the removed particles in a safe location so that they cannot be returned and redeposit themselves on the tape or other parts of the magnetic tape system.